netdev - Re: [PATCH net-next 3/3] net/sched: Introduce act

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Date:   Mon, 22 Aug 2016 21:15:41 +0300
From:   Or Gerlitz <gerlitz.or@...il.com>
To:     Amir Vadai <amir@...ai.me>, Jiri Benc <jbenc@...hat.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Linux Netdev List <netdev@...r.kernel.org>,
        John Fastabend <john.r.fastabend@...el.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        Hadar Har-Zion <hadarh@...lanox.com>
Subject: Re: [PATCH net-next 3/3] net/sched: Introduce act_iptunnel

On Mon, Aug 22, 2016 at 5:38 PM, Amir Vadai <amir@...ai.me> wrote:
> This action could be used before redirecting packets to a shared tunnel
> device, or when redirecting packets arriving from a such a device

nit, add period


> The action will release the metadata created by the tunnel device
> (decap), or set the metadata with the specified values for encap
> operation.

Jiri B. -- SB pointer to the code


> +static int tcf_iptunnel(struct sk_buff *skb, const struct tc_action *a,
> +                       struct tcf_result *res)
> +{
> +       struct tcf_iptunnel *t = to_iptunnel(a);
> +       int action;
> +
> +       spin_lock(&t->tcf_lock);
> +       tcf_lastuse_update(&t->tcf_tm);
> +       bstats_update(&t->tcf_bstats, skb);
> +       action = t->tcf_action;
> +
> +       switch (t->tcft_action) {
> +       case TCA_IPTUNNEL_ACT_DECAP:
> +               skb_dst_set_noref(skb, NULL);
> +               break;
> +       case TCA_IPTUNNEL_ACT_ENCAP:
> +               skb_dst_set_noref(skb, &t->tcft_enc_metadata->dst);

Jiri B > I understand the motivation for the decap action. However, what would
Jiri B > happen if someone does not include it?

The MD set by the (say) vxlan device will not be "consumed" (cleared)
and would be keep travelling with the SKB

> +
> +               break;
> +       default:
> +               BUG();

no, please, scream if you want to go beyond warning but don't kill and don't die

> +       }
> +
> +       spin_unlock(&t->tcf_lock);
> +       return action;
> +}